Conventional electronic cigarette usually includes an inhalation rod and a battery rod. In the inhalation rod disposes an e-liquid cup for storing e-liquid and an atomizer used to vaporize e-liquid to aerosol. The inhalation rod is usually made of opaque material. Because the battery rod is disposed at one end of the inhalation rod, makes the length of the whole electronic cigarette very long, occupying space; moreover, because a housing of the inhalation rod is made of non-transparent material, it is not convenient to observe balance of the e-liquid in the inhalation rod, thus it may occur that phenomenon of the e-liquid being dried out by the atomizer, even produce unpleasant pungent burning smell.